There was college student who was always silent and alone. He always seemed bit nervous and didn't even had any friends. His teacher noticed this and one day asked him to meet him after class. When student went to see teacher, teacher said to him, "I see that you are often very quiet. neither do you talk to anyone nor you show interest in anything and it's effect can be seen in your studies too. what is reason for this?"Student replied, "Sir, I had very difficult life. I had to face some very sad incidents in my life and I keep thinking about them. because of this I am not able to concentrate on anything and don't even feel like talking to anyone."Teacher carefully listened to student story then thought for a while and invited student to his home. On decided day, student reached teacher's home on time. "Would you like some lemonade?", teacher asked him. Student hesitatingly replied, "Yes."Teacher went inside and while preparing lemonade, he deliberately added more salt and kept quantity of sugar low. Teacher bought lemonade for him. Student made a strange face, as soon as he drank a sip of that lemonade. Seeing this teacher asked, "What happened? you didn't like it?"Student replied, "It's just there is a bit too much salt in it.."Teacher stopped him and said, "Oh.. you can't drink it.. I will throw it away."After saying this, as teacher was lifting the glass to take away, student stopped him and said, "Sir, you don't need to throw it away. it have just bit of extra salt in it, if we add a little more sugar then it will be perfectly fine to drink."Listening to this teacher smiled and said, "This is what I wanted to hear from you. now, compare this situation with your life.now understand this, to improve the taste of lemonade, we do not remove salt from it but we can fix its taste only by adding more sugar to it.likewise, we cannot separate tragic events from our life that have already happened to us but we can erase old bitterness and sorrow by adding sweetness of good experience in our life.if you keep on crying about your past, neither your present will be right nor the future will be bright."When teacher was finished talking, student realized his mistake and vowed to give the right direction to his life. 
Often, we keep looking at the closed door for so long that, we do not even pay attention to good things happening around us. One should learn to forget about past sad experiences and try to give new direction to life. 